Premium video content for our Spaceflight Now Plus subscribers.Mounted atop Atlas 5After reaching Lockheed Martin's Vertical Integration Facility following the early morning drive across the Cape, a crane lifts the New Horizons spacecraft into the 30-story building for mounting atop the awaiting Atlas 5 vehicle.Play videoLeaving the hangarThe New Horizons spacecraft, mounted atop a special transporter, departs Kennedy Space Center's Payload Hazardous Servicing Facility after spending three months in the building undergoing testing, final closeouts, filling of its hydrazine fuel, mating with the third stage kick motor and spin-balance checks. The probe was driven to the Atlas 5 rocket's assembly building at Complex 41 for mating with the launcher.Play videoMission logoWith New Horizons enclosed within the Lockheed Martin Atlas 5 rocket's nose cone, a large decal reading: "New Horizons: Pluto-Kuiper Belt Mission" is applied to the payload fairing.Play videoNose cone encapsulationThe New Horizons is packed away for its launch to Pluto as workers slide the two-piece Atlas 5 rocket nose cone around the spacecraft at the Kennedy Space Center Payload Hazardous Servicing Facility. The Swiss-made shroud protects the spacecraft during ascent through Earth's atmosphere.Play videoScience of New HorizonsThe first robotic space mission to visit the distant planet Pluto and frozen objects in the Kuiper Belt is explained by the project's managers and scientists in this NASA news conference from the agency's Washington headquarters on Dec. 19.Dial-up | BroadbandBecome a subscriberMore video

BY JUSTIN RAY
Follow the countdown and launch of the Lockheed Martin Atlas 5 rocket with NASA's New Horizons spacecraft bound for Pluto and beyond. Reload this page for the latest on the mission.

Additional coverage for subscribers:VIDEO:
LIFTOFF OF NEW HORIZONS! SHORT | LONGERVIDEO:
LAUNCH AS SEEN FROM THE PRESS SITE PLAYVIDEO:
UCS-15 TRACKING CAMERA VIEW OF LAUNCH PLAYVIDEO:
CAMERA ANGLE FROM ATOP ROOF OF THE VAB PLAYVIDEO:
ALL FIVE SOLID ROCKET BOOSTERS JETTISON PLAYVIDEO:
NEW HORIZONS IS DEPLOYED FROM THIRD STAGE PLAYVIDEO:
POST-FLIGHT INTERVIEW WITH NASA LAUNCH MANAGER PLAYVIDEO:
WATCH POST-LAUNCH NEWS BRIEFING DIAL-UP | BROADBANDAUDIO:
LISTEN TO THE NEWS CONFERENCE FOR iPODVIDEO:
NARRATED FOOTAGE OF ATLAS 5'S LAUNCH CAMPAIGN PLAYVIDEO:
NARRATED FOOTAGE OF NEW HORIZON'S CAMPAIGN PLAYVIDEO:
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THURSDAY, JANUARY 19, 20062245 GMT (5:45 p.m. EST)
This was the seventh flight of Lockheed Martin's next-generation Atlas 5 rocket, all of which have been successful. It also extends the string of successful missions by the Atlas family to 78 dating back to 1993.

"Today's launch once again demonstrates the capabilities and
flexibility of the Atlas 5," said Mark Albrecht, president of the International Launch Services firm that markets the Atlas. "This mission had a need for speed, so we provided our biggest and most
powerful vehicle. This was our seventh Atlas 5 flight, and the second Atlas 5 mission for NASA. We're proud that Atlas vehicles of all configurations have launched a total of 135 NASA missions."

The next Atlas 5 is scheduled for mid-April to launch the commercial Astra 1KR direct-to-home television broadcasting satellite.

2225 GMT (5:25 p.m. EST)
Our first batch of pictures from today's launch is available here.

2134 GMT (4:34 p.m. EST)
"Today, NASA began an unprecedented journey of exploration to the ninth planet in the solar system," says Dr. Colleen Hartman, Deputy Associate Administrator for NASA's Science Mission Directorate,
Washington, D.C. "Right now, what we know about Pluto could be written on the back of a postage stamp. After this mission, we'll be able to fill textbooks with new information."

"The United States of America has just made history by launching the first spacecraft to explore Pluto and the Kuiper Belt beyond," says Dr. Alan Stern, New Horizons principal investigator, from Southwest Research Institute in Boulder, Colo. "No other nation has this capability. This is the kind of exploration that forefathers, like Lewis and Clark 200 years ago this year, made a trademark of our nation."

"This is the gateway to a long, exciting journey," says Glen Fountain, New Horizons project manager from Johns Hopkins University Applied Physics Laboratory. "The team has worked hard for the past four years to get the spacecraft ready for the voyage to Pluto and beyond, to places we've never seen up close. This is a once-in-a-lifetime opportunity, in the tradition of the Mariner, Pioneer, and Voyager missions to set out for first looks in our solar system."

2118 GMT (4:18 p.m. EST)
New Horizons principal investigator Alan Stern confirms that ashes of Pluto discoverer Clyde Tombaugh are aboard the spacecraft. The American astronomer found Pluto in 1930.

2109 GMT (4:09 p.m. EST)
NASA's Deep Space Network tracking station in Canberra, Australia acquired the first signals from the newly-launched New Horizons spacecraft at 2:50 p.m. EST, about five minutes after the third stage separation. Telemetry from the probe indicates all systems are operating normally, project manager Glen Fountain says.

The RTG nuclear power source aboard the craft is generating 180 watts right now. That will build up to 240 watts during the next few hours. Over 200 watts of power will be expected when New Horizons reaches Pluto.

2104 GMT (4:04 p.m. EST)
"The United States has a spacecraft on its way to Pluto, the Kuiper Belt and then the stars. This is really a historic day," New Horizons principal investigator Alan Stern says.

2010 GMT (3:10 p.m. EST)
A supercharged Atlas 5 rocket carrying NASA's Pluto-bound New Horizons probe roared to life and vaulted away from Earth today on a three-billion-mile, nine-year voyage to the frigid edge of the solar system. Read our full story.

1950 GMT (2:50 p.m. EST)
NASA Launch Manager Omar Baez says today's launch of New Horizons spacecraft has been a success. The probe appears to be right on the mark.

A post-launch press conference is coming up in about an hour to provide more information on the spacecraft's health and status.

Stay tuned for continuing coverage including lots of video clips and photo galleries.

1946 GMT (2:46 p.m. EST)
New Horizons will fly past Jupiter next February, receiving a sling-shot boost from the giant planet's gravity to speed the trip to the outskirts of the solar system. The spacecraft will make its close encounter with Pluto on July 14, 2015.

1944 GMT (2:44 p.m. EST)
T+plus 44 minutes, 55 seconds. SPACECRAFT SEPARATION! The New Horizons spacecraft has been released from the third stage! The probe has departed Earth for its voyage to Pluto and the Kuiper Belt.

1935 GMT (2:35 p.m. EST)
T+plus 35 minutes, 30 seconds. Just under four minutes left in this firing of the RL10 engine. After the Centaur completes this burn, the solid-fuel third stage will spin up and separate with the New Horizons spacecraft. The third stage then ignites to accelerate the probe to Pluto.

1929 GMT (2:29 p.m. EST)
T+plus 29 minutes, 59 seconds. Centaur is firing again! The single RL10 engine has reignited as planned for a nine-and-a-half minute burn to accelerate New Horizons out of Earth orbit for the journey across the solar system. This firing will put the orbit out to the asteroid belt.

1910 GMT (2:10 p.m. EST)
T+plus 10 minutes, 12 seconds. MECO 1. Centaur's main engine has cut off following its first burn this morning. The rocket will coast in this preliminary orbit for about 20 minutes before the RL10 is reignited to propel New Horizons out of Earth orbit.

1904 GMT (2:04 p.m. EST)
T+plus 4 minutes. Less than a half-minute remaining in the first stage burn. The rocket is 67 miles in altitude, 78 miles downrange and traveling at 9,800 mph.

1903 GMT (2:03 p.m. EST)
T+plus 3 minutes, 50 seconds. The two-halves of the Atlas 5 rocket nose cone encapsulating the New Horizons spacecraft have separated. The Pluto-bound probe is now exposed to space. Also jettisoned was the Forward Load Reactor, a two-piece deck that rings the Centaur stage to support the bulbous fairing during launch.

Eight seconds after the shroud jettison, the RD-180 engine will throttle up to 100 percent again until reaching 5 G's. Throttle eases back to hold the five times gravity until 11 seconds before engine cutoff. It then throttles down to 4.6 G's to sense propellant depletion for engine shutdown.

1903 GMT (2:03 p.m. EST)
T+plus 3 minutes. No problems have been reported during this seventh launch of Lockheed Martin's Atlas 5 rocket. The rocket is 50 miles up, 59 miles downrange and traveling at 6,800 mph.

1902 GMT (2:02 p.m. EST)
T+plus 2 minutes. The Atlas 5 continues powering to space solely on the RD-180 first stage main engine now. The powerplant will keep its throttle setting at 100 percent until reaching 2.5 G's acceleration. Then the engine ramps down the throttle to maintain two-and-a-half times gravity through jettison of the rocket's nose cone, expected about 85 seconds from now.

1901 GMT (2:01 p.m. EST)
T+plus 1 minute, 55 seconds. All five solid rocket boosters have been jettisoned from the Atlas 5, having completed their job of adding a powerful kick at liftoff. The Aerojet-made boosters are the world's longest single-segment solids.

1901 GMT (2:01 p.m. EST)
T+plus 100 seconds. The five solid rocket boosters have burned out. They will remain attached to the vehicle for a little while longer, with two separating at T+plus 1 minute, 47 seconds and the other three spent casings jettisoning one-and-a-half seconds later.

1901 GMT (2:01 p.m. EST)
T+plus 75 seconds. Main engine is throttling down to 75 percent is preparation for burnout of the solid rocket boosters. After the five solid-propellant motors have consumed all of their fuel and that burnout detection is made, the Atlas 5 will throttle the RD-180 engine back to 100 percent thrust.

1901 GMT (2:01 p.m. EST)
T+plus 60 seconds. One minute into the flight of Atlas 5 and New Horizons. The rocket is roaring skyward on a mission to give humanity its first up-close look at the planet Pluto.

1900 GMT (2:00 p.m. EST)
T+plus 45 seconds. The RD-180 first stage engine is throttling up to 86 percent. The Max Q region has been passed and the greater thrust will increase the rocket's control authority and performance.

1900 GMT (2:00 p.m. EST)
T+plus 20 seconds. The main engine is easing back to two-thirds throttle to help the vehicle's passage through the area of maximum aerodynamic pressure.

1900 GMT (2:00 p.m. EST)
LIFTOFF! Liftoff of the Atlas 5 rocket launching New Horizons to Pluto and beyond -- the first mission of exploration to the outer frontier of our solar system!

1858 GMT (1:58 p.m. EST)
T-minus 90 seconds. Launch control system is enabled. The Flight Termination System has been armed.

1858 GMT (1:58 p.m. EST)
T-minus 1 minute, 50 seconds. The automatic computer sequencer is in control of all the critical events through liftoff.

1858 GMT (1:58 p.m. EST)
T-minus 2 minutes. The Atlas first stage and Centaur upper stage are now switching to internal power. Liquid oxygen and liquid hydrogen topping for Centaur will be stopped in about 10 seconds.

1857 GMT (1:57 p.m. EST)
T-minus 3 minutes. The Atlas first stage liquid oxygen replenishment is being secured so the tank can be pressurized for flight. Also, the RP-1 tank is being pressurized to flight level.

1842 GMT (1:42 p.m. EST)
A firm launch time target has not been established yet. But officials are looking at 1:55 p.m. as the earliest.

1840 GMT (1:40 p.m. EST)
Engineers are loading an updated flight profile into the rocket's guidance computer based on the latest upper level winds. This is necessary because the preview profile expired at 1:45 p.m.

1831 GMT (1:31 p.m. EST)
The clouds are still the problem. The Range had reported its approval for launch at 1:40 p.m., then a few minutes later said the cloud ceiling rule would prevent liftoff at the latest in a series of new launch times set today.

1831 GMT (1:31 p.m. EST)
Range is 'no go' now!

1829 GMT (1:29 p.m. EST)
Range is 'go' for launch! The cloud conditions are now acceptable, safety officials have determined.

1827 GMT (1:27 p.m. EST)
The new timeline calls for the launch team readiness poll at 1:33 p.m., resumption of the countdown at 1:36 p.m. and liftoff at 1:40 p.m. EST (1840 GMT), if the clouds will allow.

1825 GMT (1:25 p.m. EST)
The cloud rule at issue here in the ceiling limit. Range Safety requires that it can track the rocket unobstructed through the first 6,000 feet of flight.

1802 GMT (1:02 p.m. EST)
Veteran launch conductor Ed Christiansen, seated in the Atlas Spaceflight Operations Center four miles from the pad, has polled the various console operators to ensure all systems are ready to proceed with the countdown. The 'go' status was passed to launch director Jerry Jamison located above and behind the launch team in the management room.

The launch will be stopped at T-minus 60 seconds if clouds remain "no go."

1801 GMT (1:01 p.m. EST)
The cloud ceiling rule is in violation at the moment.

1800 GMT (1:00 p.m. EST)
Eight minutes from liftoff time.

1758 GMT (12:58 p.m. EST)
NASA launch manager Omar Baez has polled the agency oversight team. There are no problems being reported with the Atlas 5, New Horizons spacecraft or ground systems. "NASA is ready to release the hold at T-minus 4 minutes," Baez said.

1757 GMT (12:57 p.m. EST)
A break in the clouds seems to be moving overhead. There is hope of launching on-time today, if the weather will cooperate.

1755 GMT (12:55 p.m. EST)
The New Horizons team reports the spacecraft is ready to proceed with launch.

1752 GMT (12:52 p.m. EST)
All three cryogenic fuel tanks aboard the rocket are now reported at flight level.

1752 GMT (12:52 p.m. EST)
The fuel-fill sequence for the first stage main engine is reported complete.

1750 GMT (12:50 p.m. EST)
The cloud deck over the pad is creating a ceiling at 3,500 feet, the launch weather officer says. He expects there to be the opportunity for the clouds to scatter out during the window. There is a launch rule calling for the ceiling to be no lower than 6,000 feet.

1748 GMT (12:48 p.m. EST)
Twenty minutes to go.

1747 GMT (12:47 p.m. EST)
The latest guidance and steering data have been loaded into the rocket's flight computer based on today's upper level wind conditions.

1738 GMT (12:38 p.m. EST)
Now 30 minutes from launch. Flight control final preps are complete.

1656 GMT (11:56 a.m. EST)
First stage liquid oxygen tank is now half full. Chilled to Minus-298 degrees F, the liquid oxygen will be used with RP-1 kerosene by the RD-180 main engine on the first stage during the initial four-and-a-half minutes of flight today. The 25,000 gallons of RP-1 were loaded into the rocket on Monday.

1655 GMT (11:55 a.m. EST)
Chilldown of the liquid hydrogen system is now complete, allowing the super-cold fuel to begin filling the Centaur upper stage.

1641 GMT (11:41 a.m. EST)
Ten percent of the first stage liquid oxygen tank has been filled so far. The stage's bronze skin is icing over as the super-cold liquid oxygen flows into the vehicle.

1638 GMT (11:38 a.m. EST)
Now 90 minutes to launch. The Centaur liquid oxygen tank has now reached the 95 percent level. The topping off process is starting.

1637 GMT (11:37 a.m. EST)
The Atlas first stage liquid oxygen loading is transitioning from the slow-fill to the fast-fill mode.

1632 GMT (11:32 a.m. EST)
The chilldown conditioning of liquid hydrogen propellant lines at Complex 41 is now starting to prepare the plumbing for transferring the Minus-423 degree F fuel into the rocket. The Centaur holds about 13,000 gallons of the cryogenic propellant.

1628 GMT (11:28 a.m. EST)
The chilldown conditioning of the systems for the first stage liquid oxygen tank have been completed. And a "go" has been given to begin pumping super-cold liquid oxygen into the Atlas 5's first stage. The Atlas liquid oxygen tank is the largest tank to be filled today. It holds about 50,000 gallons of cryogenic oxidizer for the RD-180 main engine.

1611 GMT (11:11 a.m. EST)
Following the thermal conditioning of the transfer pipes, filling of the Centaur upper stage with 4,300 gallons of liquid oxygen has begun at Cape Canaveral's Complex 41.

The liquid oxygen -- chilled to Minus-298 degrees F -- will be consumed during the launch by the Centaur's single RL10 engine along with liquid hydrogen to be pumped into the stage a little later in the countdown. The high-energy Centaur will perform two firings today to propel the New Horizons spacecraft out of Earth orbit.

1606 GMT (11:06 a.m. EST)
The Centaur liquid oxygen pad storage area has been prepped. The next step is conditioning the transfer lines, which is now beginning to prepare the plumbing for flowing the cryogenic oxidizer.

1603 GMT (11:03 a.m. EST)
Today's launch window extends from 1:08 to 3:07 p.m. EST. However, there will be two points in time in which liftoff cannot occur because the rocket's trajectory would take it too close another object already in space. Those Collision Avoidance blackout periods, or COLAs, are 1:20 and 2:55 p.m. EST.

1558 GMT (10:58 a.m. EST)
Chilldown thermal conditioning of the mobile launch platform upon which the rocket stands is beginning. This is meant to ease the shock on equipment when supercold cryogenic propellants start flowing into the rocket a short time from now.

1558 GMT (10:58 a.m. EST)
T-minus 120 minutes and counting! Countdown clocks are running again for launch of the Atlas 5 rocket and New Horizons headed for Pluto. Clocks have one more built-in hold planned at T-minus 4 minutes. That pause will last 10 minutes, giving the launch team one last chance to catch up on work running late or deal with any problems.

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